Means for eliminating internal stresses in wire



Feb. 28, 1933. A. v. DE FOREST MEANS FQR ELIMINATING INTERNAL STRESSESIN WIRE Original Filed Feb. 17., 1928 IN VEN TOR.

Alf/ ed l/deFonesz' A TTORNEY proved Patented Feb. 28, 19331- UNITED,

PATENT OFFICE ALFRED V. DE 'FOREST OF SOUTHPORT, CONNECTICUT, ASSIGNOR'10 AMERICAN CHAIN COMP-ANY, INC; A CORPORATION Oil? NEW YORK I I MEANSroe nijminnrinenvrmnnn :STBESSES nrwmn Original applicationfilediebruary '17, 1928, SerialNo. 255,153, new Iatent No. 1,787,936,dated J'anuary 6,v

- 1931. Divided and-this application filed January 16, 1929. Serial No.332,762. 1

The present invention relates ,to an immeans for eliminating internalstresses in wire, and is a division of a copending applicationSerra-1N0. 255,153, filed ,February 17,1928. t l x a A specificapplication of the present invention is to be found in the cables'ofsuspension bridges. It is customary to'yfofrm such cables of ..a numberof strands, each strandhbeing, formed of a continuous wire which iscarried. by a trolley back and forth from anchorage to anchorage "untilthe defsired number'o'f wire lengths for afis trand have been spun. Eachwire length is subjected to tension as'soon as it is'spun and is thenlooped aboutan anchorage shoe. Q When the strand has been completed, theanchorage shoe is inserted between a pair of eye bars or other anchoragemeans and attached thereto, after which-it is drawn back by any suitablemeans such as an hydraulic j ackto adjust the strand as awhole to [apredetermined tension or sag. Y

However, internal stresses are introduced into the wire by bending itaround an anchorage shoe, which stresses are by no means negligible evenin cold drawn wire and which, in the ease of 'heat-treated'wire, are soserious as to preclude the use offbeattreated' metal for the tensionmembers of suspension bridges.

elasticity and high yield point as compared with cold worked products.'-When such wire is bent around relatively small diameters such as theshoe at the anchorage of thesuspension bridge, a very high stress isintroduced by this bendingin the outside fibres of the wire. If, aswould usually be the case, this bend were beyond the elastic limit ofthewire, the outside fibres would already be loaded with their-fullestcapacitybeforeany reduce the load on" the wire at'tbis pointto Theessential quality 'of heat-treated metal is its high modulus of the,same'figure as that in the straight portions of the'wire. A morespecific object ofthe invention is to provide means for forming ananchorage loop in a wire in which the outside fibres of the wire, arepermanently stretched and the inside fibres are permanently'compressed,so that the forces across any section will be zero, as they arein thestraight portionof the wire. In other words,

elastic limit will be temporarily lowered so that it may becsubjected'to a considerable amount of deformation, and after this deformation anaging effect will take place which will in time restore the full elasticproperties of the wire. that heat-treated steel may have 'its'elastic'It is well known" l6 limits temporarily'lowered by subjecting thematerial to over-stressing and that the full elastic properties willbe'restored' in time by an aging effect. 7

Another object of the invention is to provide means for applying aprotective metallic coating on the loop end of the strand,this coatingbeing applied in molten conditionat a temperature that will insure acertain amount of heat treatment to eliminate the in- I ternalstresseswhich may be presentqin the wire and tohasten the aging effect whichwill restore the wire to its full elastic properties.

With these and other objects in view which will appear hereinafter, theinvention will now be described in connection with the accompanyingdrawing and thereafter the novelty andscope 'ofthe invention willbepoint ed outin the claims.

In the drawing: Figure l is a somewhat .diagrammatical plan View of astrand anchorage illustrating themeansused for preforming aloop ina wirebefore it is shoe.

, l' d t th ho app 1e 0 e anc rage vt Fig. 5 is a view in cross-sectionof a ortion of the anchorage shoe taken in the p ane 55 of Fig. 4% andv1ewed in the dlrection of the arrows.

The simplest method of preforming a loop in the wire before the wire isapplied to the anchorage shoe, is to seize the wire length ad jacenttheanchorage shoe in a suitable'clamp,

'after it has been subjected to the requisite preliminary tension, andthen to form a loop in the wire by bending it around a stud or pulley ofsmaller diameter than that of the shoe. The wire is thus bent beyond itselastic limit, permanentlystretching the outside fibres and compressingthe inside fibres, and the diameter ofthe stud is such that when thewire is released from the stud it will spring out to a diameter equal tothat of the shoe, having taken a permanent set of such diameter. Theinternal stresses are thus overcome and, in time, the wire will resumeits original elastic limit which was temporarily 1owered by bending itbeyond its yield point. The preformed loop is then transferred to theanchorage shoe.

Another process of preforming a loop of requisite diameter isillustrated in Fig. 1. In this figure, which is a plan view, ananchorage shoe is shown which is formed with a peripheral channel orgroove to receive Wires 11 of the strand. The shoe is rounded at therear end about which the wires are to be bent, that is, the left-handend as viewedin Fig. 1. The shoe 10 is temporarily secured in fixedposition by a lug or other means introduced through an opening 12therein, said means not being shown in the drawing.

As a wire length is spun across thebridge to the anchorage, it issubjected to tension by any well known means and then is clampedadjacent to the shoe 10 by means of a clamp 15. This clamp may be of anydesired form, but is here shown as consisting of a pair of jaws 13 and14:, the former being stationary and engaging one side of the wire whilethe j aw 14: slides in the frame of the clamp and may be adjustedagainst the opposite sid of the wire by means of a bolt 16.

Adjacent the shoe there is a fixed stud 17, which carries a pulley 18.Mounted on the stud 17 is an arm 19 formed with a handle 20 and on thearm 19 are three rollers 21. These rollers are relatively staggered soas to engage opposite sides of the wire 11 and pr0- duce reverse bendstherein after the manner of a wire straightener. Thus, after thewire hasbeen clamped between the jaws 13 and 14, it is threaded between therollers 21, and the handle 20 is then operated to swing the arm 19 withthe rollers about the stud 17 The rollers bend the wire beyond itselastic limit and as the handle 20 is swung around the stud 17, the wire11 is formed into a loop which passes about the pulley 18. In thismanner the wire 11 is bent into a loop which takes a permanent set,because of the over stressing produced by the rollers 21. Tl e preformedloop is then taken out of the rollers 21 and off the pulley 18 andtransferred to the adjacent shoe 10. The wire length beyond the 100 maythen be conveyed, by the trolley, to t e opposite anchorage of thebridge, where,by the same process a loop is preformed inthe wire beforeit is applied to the anchorage shoe at that end. Thus the strand isbuilt up of a number of lengths of wire, each having a preformed looptherein in which'the internal stresses have been eliminated.

Another system is shown in Fig. 2 in which corresponding numerals areused. to indicate corresponding parts. In this instance, however,instead of preforming loop, the wire is subjected to treatment whichtemporarily re duces its elastic limit. Adjacentthe shoe 10 is asupport25 on which is mounted number of rollers 26. These rollers are arrangedin an upper and a lower series, somewhat like the rollers of a wirestraightener, so as to produce bends in the wire. However, the rollersat the rear end of the support 25, that is the left hand end, as viewedin Fig. 2, are closer together, producing sharper bends in the wire thanthose near the right hand end. There is thus a tapering off of thebending operation so that the wire, after passing through the series ofrollers, is left free of internal stresses. Preferably, the support 25is made in two parts which are hinged together at one end as indicatedat 27 and are clamped together at the opposite end by means of the clamp28. The upper series of rollers 26 is supported on the upper section ofthe support 25 and lower series on the lower section. The wire is thenlaid on the lower rollers and the two sections are swung together andclamped, causing the upper rollers to bite into the wire and press itover and between the lower rollers. The support 25 is then crawn towardthe left as Viewed in Fig. 2 so as to sub ject the wire to repeatedbendings of such magnitude as to exceed the elastic limit of the wireand by. such working temporarily to reduce brittleness or hardness ofthe wire. This done, the wire is seized in the clamp 15, after which thesupport 25 is opened. Then the wire may be readily bent around the shoe10 without introducing any serious internal stresses therein. Anadvantage of thus working the wire before forming the loop is that theexact radius over which the wire is bent an aging process takes placewhich restores is of no particular importance and there is no danger ofweakness due to inexactness of the location of the tangent between thestrain portion of the wire and the beginning of the curvature. After theloop has been formed,

thefull elastic properties to the wire.

Fig. 8 shows still another method of temporarily reducing theelasticlimit of that portion of the wire which is to be looped about theanchorage shoe. On the anchorage shoe 10 is mounted a form 30, such as apulley,-

about which an incoming wire is bent. The wire, after passing about theform 30, is attached to a tension means 31, such as a block and tackle,by which the wire may be drawn up to the desired preliminary tension sothat it will lie parallel to other wires in the strand. The diameter ofthe form is such that the wire on being drawn thereabout is bent beyondits elastic limit to such an extent as to take a fixed curvaturecorresponding to the curvature of the shoe 10. After the wire has beengiven this curvature, it is held in advance of the form 30 by the clamp15 to 'maintain said preliminary tension in the main body of the wirewhile tensioningmeans 31 is released. The curved portion of the wire isthen transferred to the shoe '10.

The length of wire subjected to the bending process by drawing it aboutthe form 30 is considerably greater than the length of the curvedportion of the shoe about which the wire loop is to be fitted. It isnecessary, therefore, to eliminate the curvature in that part of thewire which extends beyond the curved part of the shoe. This is done bypassing the wire, after it leaves the form 30, in a reverse bend about asecond form 32, also mounted on the anchor shoe. The form 32 is solocated with respect for form 30 that the length of wire from the pointat which it begins to bend about the pulley 30 to the point at which itbegins to bend about the form 32 equals the length of the curved part ofthe shoe.

The curve thus formed in the wire corresponds not only to the curvatureof the shoe but also the length of said. curvature.

' Furthermore, the pulley 30 is so positioned that the wire willbecur-ved in the proper location to coincidewith the curved part of theshoe.

Fig. 4 shows the shoe turned at right angles and secured between a pairof eye bolts 33 by which the shoe is seized and drawn backward tosubject the strand as a whole tothe requisite tension. A stud 34 passesthrough the eye bolts and also through the opening 12 The shoe andstrand, loop are'then heated and molten lead is poured into theperipheral recess around the wires 11. The lead is main-' tained at suchtemperature and introduced and said tensioning means.

After this, the strand may be subjected-to the necessarytension bydrawing on the eye bolts 33 so as to raise the strand to thepredetermined sag of the finished.cable.-

While particular reference has been made herein to the application ofthe present in vention to bridge strands and cables, and tohigh'tens'ile' heat-treated wire, obviously the invention is not limitedto suchwire nor to such application, but can .be used in the loop- I ingof anytensi'on member in rod orwire form and in which it is desirable toeliminate I internal stresses. j Having thus described my invention,what. I claim and desire to protect by Letters Patentisr i 7 1. Means.for forming at one end of a run of wire whose other end is anchored,astress free anchorage loop to fit a seat in an anchorage, which meanscomprises a form, means for drawing the wire topredeterminedtensionabout the form to produce a loop, and means for temporarilyclamping the wire in advance of the form afterthe-wire has been freeanchorage loopto fita curved seat inan I anchorage, which meanscomprises ;aformadjacent said seat'and about which said wire may bebent, tension means for subjecting the wire to a predetermined tensionby drawing it about the form, said formbeing ,of such shape and at suchlocation with respect to the seat that the wire drawnabout the form willassume a fixed curvature substantially equal to that of the seat andcorersponding in location to that of these'at when the wire is H undersaid tension, and a second form between the first mentioned form andsaidtensioning means about which the wire maybe reversely bent to straightenthat portion of the wire which lies between said second form 3. Meansfor forming'at one end of a run of wire whose other end is anchored, astress free anchorage loop to fit a curved seat in an anchorage shoe,which .meanscomprises a 5 form mounted. on the shoeandabout which thesaid wire maybe bent to form a loop, means for subjecting the wire to apredetermined tension by drawing the wire about the form, said i'orrnbeing of such shape that the wire drawn thereaboutwill assume a fixedcurvature substantially equal tothat of the seat and at alocationcorresponding to that of the seat when the Wire is under said tens sion,and a second form also mounted on the shoe between the first form andthe tensioning means and about which the wire may be reversely bent tostraighten that portion of the wire which lies between the second formand the tensioning means. J

4. Means for forming at one end of a run of wirewhose other end isanchored, astress free anchorage loop to fit a curved seat in ananchorage shoe, which means comprises a pair of rotary formsadjacentsaid seat about one of which the wire is bent in one directionand about the other of which the wire is bent in the opposite direction,and means for drawing the wire about said forms, the diameter of of wirewhose other end is anchored, a stress free anchorage loop to fit acurvedseat in an anchorage shoe, a pair of forms adjacent said seat about oneof which the wire is bent in one direction and about the other of whichthe wire is bent in the opposite direction, means for drawing the wireunder tension about said forms, and a clamp for holding the wire inadvance of the forms after it has been tensioned, the diameter of thefirst of said forms being such as to give the wire a fixed curvaone ofwhich the wire is bent in one direction and about the other of which thewire is bent in an opposite direction, the diameter of the first of theforms being such as to give the wire a fixed curvature corresponding tothat of the seat, and the diameter and position of the specification.

ALFRED V. DE FOREST.

ture corresponding to, that of the seat and at a location alsocorresponding to that of the seat when the wire is under said tensionand the diameter and relative position of the other form beingsuch as tostraighten all the wire curved by the first form except such portion asis required to fit upon said seat.

6. Means for forming atone end of a run of wire whose other end isanchored, a stress free anchorage loop to engage a curved anchorageseat, which means comprises a plurality ofrollers adjacent said seatbetween which the wire may be drawn, the rollers being in such relativeposition as to reversely bend beyond its elastic limit that portion ofthe wire which is to form the loop prior to passing the Wire about theseat, and means for clamping the runof wire in advance of the anchorageafter it has been drawnto predetermlned tension between said rollers.

7. Means for forming a stress free anchorage loop to fit an anchoragewhich comprises a pair of forms adjacent the anchorage about

